Term
|
Definition
| meaning change, pertains to all chemical and physical workings of cells; term that can be used to designate almost any physiological process. |
|
|
Term
|
Definition
| larger molecules are degraded or broken down into smaller molecules, usually with the release of energy; The chemical breakdown of complex compounds into simpler units to be used in cell metabolism. |
|
|
Term
|
Definition
| also called biosynthesis, larger molecules are built from smaller ones, which results in the formation of cell structures. It is usually driven by energy derived from catabolism; The energy-consuming process of incorporating nutrients into protoplasm through biosynthesis. |
|
|
Term
|
Definition
| A protein biocatalyst (trigger) that facilitates metabolic reactions. The chemical reactions of life would never proceed without proteins called enzymes. Enzymes do NOT create reactions, they trigger them. Due to the free energy inherent in molecules, a reaction could occur spontaneously at some point even without an enzyme but at a very slow rate. Because most uncatalyzed metabolic reactions do not occur fast enough to sustain cell processes, enzymes are indispensable to life *BIOCHEMICAL LEVERS* |
|
|
Term
| checklist of enzyme characteristics |
|
Definition
-
Composed mostly of protein; may require nonprotein cofactors
-
Act as organic catalysts to speed up the rate of cellular reactions
-
Lower the activation energy required for a chemical reaction to proceed
-
Enable metabolic reactions to proceed at a speed compatible with life
-
Have unique characteristics such as shape, specificity, and function
-
Provide an active site for target molecules called substrates
-
Are much larger in size than their substrates
-
Associate closely with substrates but do not become integrated into the reaction products
-
Are not used up or permanently changed by the reaction
-
Can be recycled and function in extremely low concentrations
-
Are greatly affected by temperature and pH
-
Can be regulated by feedback and genetic mechanisms
|
|
|
Term
|
Definition
Measurable resistance to a reaction, which must be overcome for a reaction to proceed; The minimum energy input necessary for reactants to form products in a chemical reaction. In the laboratory, overcoming this initial resistance can be achieved by
increasing thermal energy (heating) to increase molecular velocity, increasing the concentration of reactants to increase the rate of molecular collisions, or
adding a catalyst. In most living systems, the first two alternatives are not feasible, because elevating the temperature is potentially harmful, and higher concentrations of reactants are not practical. This leaves only the action of catalysts, and enzymes fill this need efficiently and potently. |
|
|
Term
|
Definition
| The specific molecule upon which an enzyme acts. The enzyme presents a uniquely shaped pocket that fits only that particular substrate. Although an enzyme binds to the substrate and participates directly in changes to the substrate, it does not become a part of the products, is not used up by the reaction, and can function over and over again. A key to understanding the roles of enzymes in metabolism is their structure. |
|
|
Term
|
Definition
| A conjugated enzyme is a combination of a protein, now called the apoenzyme, and one or more cofactors. |
|
|
Term
|
Definition
| The protein part of an enzyme, as opposed to the nonprotein or inorganic cofactors. Like all proteins, an apoenzyme exhibits levels of molecular complexity called the primary, secondary, tertiary, and, in larger enzymes, quaternary organization. The first three levels of structure arise when a single polypeptide chain automatically folds and achieves stability by forming disulfide and other bonds. Folding causes the surface of the apoenzyme to become three-dimensional which results in the enzyme's specificity for substrates. The pocket where the substrate binds is the active site, or catalytic site, and there can be one to several sites. Each type of enzyme has a different primary structure (type and sequence of amino acids), each has variations in folding and unique active sites. |
|
|
Term
|
Definition
| An enzyme accessory. Cofactors are either organic molecules, called coenzymes, or inorganic elements (metal ions) aka metallic cofactors that many enzymes require to become functional. In some enzymes, the cofactor is loosely associated with the apoenzyme by noncovalent bonds; in others, it is linked by covalent bonds. |
|
|
Term
|
Definition
| A complex organic molecule, several of which are derived from vitamins (e.g., nicotinamide, riboflavin). A coenzyme operates in conjunction with an enzyme. Coenzymes serve as transient carriers of specific atoms or functional groups during metabolic reactions. |
|
|
Term
| Enzyme-Substrate Interactions |
|
Definition
| For a reaction to take place, a temporary enzyme-substrate union must occur at the active site. The bonds formed between the substrate and enzyme are weak and, of necessity, easily reversible. Once the enzyme-substrate complex has formed, appropriate reactions occur on the substrate, often with the aid of a cofactor, and a product is formed and released. The enzyme can then attach to another substrate molecule and repeat this action. |
|
|
Term
|
Definition
| The process by which an enzyme changes shape slightly to allow a specific substrate to "fit into" or access it's appropriate active site so that the proper reactions can occur. Once the reaction is complete, the enzyme releases the product of their union so that it may repeat the process with another molecule of the same substrate. |
|
|
Term
|
Definition
In general, metals activate enzymes, help bring the active site and substrate close together, and participate directly in chemical reactions with the enzyme-substrate complex.
ex: iron, copper, magnesium, manganese, zinc, cobalt, selenium, and many others
|
|
|
Term
|
Definition
| are organic cofactors that work in conjunction with the apoenzyme to perform a necessary alteration of a substrate. The general function of a coenzyme is to remove a chemical group from one substrate molecule and add it to another substrate, thereby serving as a temporary carrier of this group. The specific activities of coenzymes are many and varied. Several are derived from vitamins (e.g., nicotinamide, riboflavin). A coenzyme operates in conjunction with an enzyme. Coenzymes serve as transient carriers of specific atoms or functional groups during metabolic reactions. |
|
|
Term
|
Definition
| A component of coenzymes critical to nutrition and the metabolic function of coenzyme complexes. One of the most common components of coenzymes; are important to nutrition and may be required as growth factors for living things; deficiencies prevent the complete holoenzyme from forming. Consequently, both the chemical reaction and the structure or function dependent upon that reaction are compromised. |
|
|
Term
|
Definition
| transported extracellularly after initial synthesis in the cell, where they break down large food molecules or harmful chemicals (see discussion of hydrolysis reactions), Examples are cellulase, amylase, and penicillinase. |
|
|
Term
|
Definition
| retained intracellularly and function there. Most enzymes of the metabolic pathways are of this variety. |
|
|
Term
|
Definition
| are always present and in relatively constant amounts, regardless of the amount of substrate. The enzymes involved in utilizing glucose, for example, are very important in metabolism and thus are this type |
|
|
Term
|
Definition
| the production of which is either turned on (induced) or turned off (repressed) in response to changes in concentration of the substrate or product. The level of inducible and repressible enzymes is controlled by the degree to which the genes for these proteins are expressed |
|
|
